當addsubview：被調用時，UIView拖放 - 拖動視圖消失？

Question

我有DragView對象和DropView對象，它們都是UIView子類，在UIView容器中。在手勢平移上調用以下selector方法。問題是，當我將DragView對象拖到DropView對象上時，DragView對象就會消失。我不知道我做錯了什麼。

- (void)dragViewMoved:(UIPanGestureRecognizer *)gesture{ 

    CGPoint touchLocation = [gesture locationInView:self]; 

    static DragView *currentDragView; 
    static DropView *currentDropView; 

    if(UIGestureRecognizerStateBegan == gesture.state){ 

     for(DragView *dragView in self.dragViews){ 

      if(CGRectContainsPoint(dragView.frame, touchLocation)){ 
       currentDragView = dragView; 
       break; 
      } 
     } 

    }else if(UIGestureRecognizerStateChanged == gesture.state){ 

     currentDragView.center = touchLocation; 

     for(DropView *dropView in self.dropViews){ 

      if(CGRectIntersectsRect(currentDragView.frame, dropView.frame)) 
       currentDropView = dropView; 

     } 

    }else if (UIGestureRecognizerStateEnded == gesture.state){ 

     if(CGRectIntersectsRect(currentDragView.frame, currentDropView.frame)){ 

      //I think the problem is happening here 
      currentDragView.center = touchLocation; 
      [currentDragView removeFromSuperview]; 
      [currentDropView addSubview:currentDragView]; 

     } 

     currentDragView = nil; 

    } 

} 

Answer 1

而不是做這個的：

currentDragView.center = touchLocation; 

試圖改變這樣的：

currentDragView.center = [gesture translationInView:currentDropView]; 

更新：

嘗試切換此行：

static DragView *currentDragView; 

要這樣：

DragView *currentDragView = gesture.view;